Fiber optic cables are used in the telecommunication industry to transmit light signals in high-speed data and communication systems. A standard fiber optic cable includes a fiber with an inner light-transmitting optical core. Surrounding the fiber typically is a reinforcing layer and an outer protective casing. A fiber terminates at a fiber optic connector. Connectors are frequently used to non-permanently connect and disconnect optical elements in a fiber optic transmission system. Connectors are typically coupled together through the use of an adaptor. An example adapter is shown in U.S. Pat. No. 5,317,663, the disclosure of which is incorporated by reference.
There are many different fiber optic connector types. Some of the more common connectors are FC and SC connectors. Other types of connectors include ST and D4-type connectors.
FIG. 1 shows an example SC connector 10 that includes a ferrule 12. The ferrule 12 is a relatively long, thin cylinder preferably made of a material such as ceramic. Other materials such as metal or plastic can also be used to make the ferrule 12. The ferrule 12 defines a central opening 14 sized to receive a fiber of a given cladding diameter. An epoxy is typically placed into the opening 14 prior to inserting the fiber to hold the fiber in place. The ferrule 12 functions to align and center the fiber, as well as to protect it from damage.
Referring still to FIG. 1, the ferrule 12 is positioned within a ferrule housing 18 typically made of a material such as metal or plastic. An outer grip 19 is mounted over the ferrule housing 18. The housing 18 is externally keyed to receive the grip 19 at a single rotational orientation. A hub assembly 20 spring biases the ferrule 12 toward the front of the connector 10. A crimp sleeve 37 and boot 28 are located at the rear of the connector 10.
As described at U.S. Pat. No. 6,428,215, which is hereby incorporated by reference in its entirety, the connector 10 can be “tuned” by rotating the ferrule 12 relative to the ferrule housing 18 until an optimum rotational position is determined, and then setting the ferrule at the “tuned” or optimum rotational orientation. Connectors are tuned to ensure that when two connectors are coupled together via an adapter, the ends of the fibers being connected are centered (i.e., aligned) relative to one another. Poor alignment between fibers can result in high insertion and return losses. Insertion loss is the measurement of the amount of power that is transferred through a coupling from an input fiber to an output fiber. Return loss is the measurement of the amount of power that is reflected back into the input fiber.
FIG. 2 shows an example FC connector 30 having a ferrule 32 mounted within a ferrule housing 34. A key 36 is fitted over the ferrule housing 34. The key 36 is positioned to correspond to a tuned orientation of the ferrule 32. An outer grip or connector 38 mounts over the ferrule housing 34. A hub assembly 40 is fixedly mounted to the ferrule 32. The hub assembly 40 spring biases the ferrule in a forward direction. The connector 30 also includes a dust cap 42 that covers the front of the ferrule 32, and a crimp sleeve 37 and boot 44 mounted at the rear of the connector 30.
In addition to tuning, insertion and return loss can be improved by polishing the end faces of the ferrules. During the polishing process, the ferrules are commonly held in a fixture, and the end faces are pressed against a rotating polishing wheel or disk. Frequently, the end faces are polished to form a polished surface oriented along a plane that is perpendicular with respect to the longitudinal axis of the fibers. However, for some applications, the end faces are polished to form a surface aligned at an oblique angle with respect to the longitudinal axis of the fibers.
Other process steps are also undertaken to complete the manufacture of fiber optic connectors. For example, after polishing, the end faces of the connector ferrules are often cleaned. Other steps include tuning the connectors, testing the connectors for insertion and return loss, and assembling the various components of the connectors.
Historically, the manufacture of fiber optic connectors has been quite labor intensive. Originally, connectors were individually manually polished and individually manually moved through the various processing steps. Manufacturing efficiency improved with the more prevalent use of multi-connector fixtures (e.g., see U.S. Pat. No. 6,396,996), which allowed multiple connectors to be simultaneously processed. While multi-connector fixtures have improved manufacturing efficiencies, further improvements in the area of automation are needed.